AWS CloudFront：缓存特定对象

Question

I have a CDN (CloudFront) distribution with the following configuration. (I use signed cookies but I don't think it's related):

    DefaultCacheBehavior:
      # Target the origin
      TargetOriginId: !Sub 'S3-${ProjectName}-${Environment}'
      ViewerProtocolPolicy: redirect-to-https
      # Check always the origin (in this case S3) for the item so always the newest item is served.
      MinTTL: 0
      DefaultTTL: 0
      MaxTTL: 0
      AllowedMethods:
        - HEAD
        - GET
        - OPTIONS
      CachedMethods:
        - HEAD
        - GET
        - OPTIONS
      ForwardedValues:
        QueryString: true
        Cookies:
          Forward: all
      # Specifies the AWS account(s) that you want to allow to create signed URLs or signed cookies for private content.
      TrustedSigners:
        - !Ref AccountID

Now I have some objects (object A) with metadata: Cache-Control: no-cache

I have some other objects (object B) with metadata: Cache-Control: max-age=604800

Now I access object A:

first access: X-Cache: Miss from cloudfront
second access: X-Cache: RefreshHit from cloudfront

Now I access object B:

first access: X-Cache: Miss from cloudfront
second access: X-Cache: RefreshHit from cloudfront

I would suspect that object B shows: Hit from CloudFront?

What am I doing wrong?

Answer 1

Your MaxTTL: 0 means that every requests from CloudFront is always proxied to the Origin. You should increase this value.

The value that you specify for Default TTL applies only when your origin does not add HTTP headers such as Cache-Control max-age, Cache-Control s-maxage, or Expires to objects.

See more in the Guide

Answer 2

AWS has a nice document on it:

https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/Expiration.html

RefreshHit from cloudfront : This means that CloudFront is still caching but it's making conditional GET with origin to know if the object has been modified or not, if it receives 304 not modified, it serves it from it's cache otherwise the origin would return a new object (in case if object has been modified).

If you look at the table mentioned in the above link , you'll understand why you're seeing RefreshHit from cloudfront for object B. The Cache-control and CloudFront TTL has correlation.